1. Field
The disclosed concept pertains generally to electrical switching apparatus and, more particularly, to circuit interrupters, such as circuit breakers.
2. Background Information
Electrical switching apparatus employing separable contacts exposed to air can be structured to open a power circuit carrying appreciable current. These electrical switching apparatus, such as, for instance, circuit breakers, typically experience arcing as the contacts separate and commonly incorporate arc chambers, such as arc chutes, to help extinguish the arc. Such arc chutes typically comprise a plurality of electrically conductive arc plates held in a spaced relation around the separable contacts by an electrically insulative housing. The arc transfers to the arc plates where it is stretched, split and cooled until extinguished.
Conventional miniature circuit breakers (MCBs) are not specifically designed for use in direct current (DC) applications. When conventional alternating current (AC) MCBs are sought to be applied in DC applications, multiple poles are electrically connected in series to achieve the required interruption or switching performance based upon the desired system DC voltage and system DC current.
One of the challenges in DC current interruption/switching, especially at a relatively low DC current, is to drive the arc into the arc chamber. Known DC electrical switching apparatus employ permanent magnets to drive the arc into arc splitting plates. A known problem associated with such permanent magnets in known DC electrical switching apparatus is unidirectional current flow operation of the DC electrical switching apparatus. A proposed solution to provide bi-directional current flow operation in a molded case circuit breaker (MCCB) is a double-break design (e.g., similar to the contact structure of a contactor) including two sets of contacts, and two separate arc chambers with a stack of arc plates for each arc chamber, where each arc chamber has a pair of magnets to generate opposite magnetic fields to drive an arc into a corresponding stack of arc plates depending upon the direction of the current. This problem and its proposed solution make it very difficult to implement a permanent magnet design for typical DC MCBs without a significant increase in size and cost.
There is room for improvement in electrical switching apparatus that can switch direct current.
There is also room for improvement in direct current arc chambers.